[llvm-commits] [llvm] r60186 - /llvm/trunk/lib/Target/README.txt

[Nick Lewycky]

Author: nicholas
Date: Thu Nov 27 16:12:22 2008
New Revision: 60186

URL: http://llvm.org/viewvc/llvm-project?rev=60186&view=rev
Log:
Add a synthetic missed optimization.

Modified:
    llvm/trunk/lib/Target/README.txt

Modified: llvm/trunk/lib/Target/README.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/README.txt?rev=60186&r1=60185&r2=60186&view=diff

==============================================================================
--- llvm/trunk/lib/Target/README.txt (original)
+++ llvm/trunk/lib/Target/README.txt Thu Nov 27 16:12:22 2008
@@ -984,3 +984,27 @@
 }
 
 //===---------------------------------------------------------------------===//
+
+These three functions all perform the same computation, but produce different
+assembly. On x86, they are sorted from slowest to fastest.
+
+define i8 @udiv(i8 %x) readnone nounwind {
+  %A = udiv i8 %x, 250
+  ret i8 %A
+}
+
+define i8 @select(i8 %x) readnone nounwind {
+  %A = icmp ult i8 %x, 250
+  %B = select i1 %A, i8 0, i8 1
+  ret i8 %B 
+}
+
+define i8 @addshr(i8 %x) readnone nounwind {
+  %A = zext i8 %x to i9
+  %B = add i9 %A, 6       ;; 256 - 250 == 6
+  %C = lshr i9 %B, 8
+  %D = trunc i9 %C to i8
+  ret i8 %D
+}
+
+//===---------------------------------------------------------------------===//